We propose to-continue a program of research with four broad objectives: 1) to utilize longitudinal measures of EEG sleep in characterizing the psychobiological substrate of recurrent major depression in late life (Study 1); 2) to utilize EEG sleep measures in identifying which types of maintenance therapy are best suited to ensure sustained remission (Study 1); 3) to establish the EEG sleep correlates of: a) nortriptyline efficacy in the treatment of bereavement-related depression; b) unresolved grief; and c) the post-treatment course of bereavement-related depression (Study 2); and 4) to establish the EEG sleep correlates of continued successful aging (Study 3). Within this context, we propose to complete three ongoing longitudinal studies of EEG sleep in: 1) 120 patients within a double-blind placebo-controlled maintenance therapies protocol which is evaluating the prophylactic efficacy of nortriptyline and interpersonal psychotherapy (Study 1); 2) 80 elders in a double-blind placebo-controlled study of the efficacy of nortriptyline in acute and continuation therapy of bereavementrelated major depression (Study 2); and 3) a control group of 77 elders who exemplify successful aging (Study 3). All three studies are conceptually linked and integrated by a focus on the homeostatic dimension of sleep-wake regulation in depression and in aging. All three utilize both biological and psychosocial measures to understand heterogeneity in late-life depression. While Studies 1 and 2 are complementary in their focus on recurrent versus first-episode elderly depressed patients, both utilize double-blind, placebo-controlled designs to study EEG sleep during illness and during remission. Hence, both utilize a controlled treatment study (maintenance therapy in Study 1, acute/continuation therapy in Study 2) to achieve psychobiological/clinical aims. Study 3, likewise longitudinal, will permit delineation of the medical, psychiatric, and psychosocial factors that impinge upon sleep in successfully aging control subjects and will also permit an investigation of the role of sleep in the maintenance of successful adaptation in late life along physical and psychological dimensions. These ongoing studies will employ survival analyses, logistic regression, and a variety of path analyses to achieve their objectives of investigating interrelationships among sleep, aging, depression, and both psychopharmacological and psychotherapeutic interventions.